1. Field of the Invention
The invention relates to an hydraulic operating arrangement, in particular for lids, doors, covers and the such on automotive vehicles, having at least one double-acting working cylinder whose working chambers are connected respectively by way of one reciprocally unlockable check valve with one side respectively of a reversible pressure medium source. The respective working chamber under pressure is connected with a proportional pressure-regulating valve for pressure control.
2. The Prior Art
In an apparatus of the kind referred to above, known for example from AT 405 749 B, the working chamber-of the working cylinder that is respectively under pressure is connected to the entry side of the proportional pressure regulating valve by way of an automatically switching reversing valve. On the basis of a system pressure curve, determined or established either empirically or in. another suitable manner, the proportional pressure regulating valve can be selected in such a way that the system pressure respectively lies only barely above the pressure that is required for the current movement phase. This delivers a large variety of advantages for operating arrangements of this type.
It is the object of this invention to improve an operating arrangement of the type described above in terms of further simplifying the apparatus""s constructive design.
This objective is achieved with an operating arrangement of the type referred to at the outset in such a way that the proportional pressure regulating valve is connected at its exit side with the pressure medium lines by way of a check valve which respectively opens in the direction of these pressure medium lines, in particular between the reciprocally unlockable check valves and the respectively associated working chamber of the working cylinder. Consequently, contrary to the described operating arrangement that is known in the art, the hydraulic medium which is directed away at the exit side of the proportional pressure regulating valve is returned directly into the pressure medium cycle and to the respective aspirating working chamber. This is why it is possible for the process to realize various advantages and improvements. Thus, with the so-called synchronism cylinder, which provides that during each movement phase the expelled hydraulic volume on the one side is equal to the hydraulic volume that is aspirated in on the other side, it is possible to work essentially without the need to compensate from the tank for lost volume. This allows reducing the size of the operating arrangement as well as the amount of the required drive power because the hydraulic volume that is expelled on the one side can directly be returned on the other side via the control action of the proportional pressure regulating valve. In most practical applications, however, a shuttle valve or something similar will be envisioned parallel to the working cylinder on the side of the tank in order to be able to quickly remove, for example, air bubbles from the hydraulic medium and to be able to suck in fresh hydraulic medium.
With the measure that has already been described in AT 405 749 B and which provides that the proportional pressure regulating valve be selected which controllably limits the system pressure taking into consideration the respective movement process of the element that is to be actuated, it is easy to effect, for example, a gentle movement take-up or correspondingly a gentle movement deceleration of the element that is to be actuated. With the normal hydraulic actuation it is possible, after the pump has stopped, to control the proportional pressure regulating valve in such a way that a holding pressure is in effect in both working chambers of the working cylinder ensuring a secure hold of the element that is to be actuated. This holding pressure can be adjusted for the respective application and can, naturally, be different for various movement positions of the element that is to be actuated.
Upon actuating the element manually, the volume flow that is to be expelled flows from the one side of the working cylinder via the proportional pressure-regulating valve and the previously mentioned check valve into the opposite, re-aspirating working chamber, which can be safely filled with the fluid while at the same time avoiding the possibility of air cushions forming in the pressure mediumxe2x80x94thus, the element that is to be actuated is always hydraulically loaded, securely and solidly. The defined pressure acting on the proportional pressure regulating valve, e.g., defined by its control or through a corresponding initial tension, must be overcome first if the actuation is manual (refer to above xe2x80x9cholding pressurexe2x80x9d). After over-pressuring of this holding pressure has occurred, it is possible to determine, for example by way of the control of the proportional pressure regulating valve or using a practice that will be described below, that a manual movement of the working cylinder has been initiated. This means that the proportional pressure-regulating valve can now be selected once again in such a way that little or no pressure drops. This is why the initiated manual actuation is possible without additional counteracting force worth mentioning. After the manual movement is complete (once again, this can be determined in various ways), the proportional pressure regulating valve can again be selected with the previous holding pressure or with another holding pressure.
If the element that is to be actuated by the working cylinder is to be opened quickly by hand, it is possible to additionally influence the control of the proportional pressure regulating valve directly for example by way of a switch, in particular in such a way that the two working chambers of the working cylinder become connected virtually without resistance in the manner described above. This in turn allows for the quick and easy manual opening of the element without any counteracting pressure that is worth mentioning. To complete this adjustment possibility the proportional pressure regulating valve can be switched back to holding pressure; and this can also take place according to a corresponding process allowing the easy realization of a gentle deceleration of the element that is to be actuated.
According to a particularly preferred embodiment of the invention it is envisioned that, in conjunction with the proportional pressure regulating valve, a preloaded check valve is placed in the connection between the two working chambers of the working cylinder, which opens respectively from the pressure medium line toward the entry of the proportional pressure regulating valve. This allows a simple and functionally safe connection in terms of construction of the respective working chamber under pressure with the proportional pressure regulating valve, avoiding the separate reversing valve that was referred to at the outset in the context of the state of the art as envisioned for this purpose.
According to another preferred embodiment of the invention the pressure level of the two working chambers can be monitored using at least one pressure sensor whose measured signal, by way of a hooked up control device, is used for controlling the proportional pressure valve. By way of this working chamber side pressure sensor, it is possible to achieve very easily that the actual system pressure be considered, including all of the information contained therein regarding the movement process, any obstacles, etc. For example, the presence of an obstacle in the actuating path can be detected by way of the corresponding pressure pulse in the system pressure and, e.g., the hydraulic can be switched off. On the other hand, by immediately opening the proportional pressure-regulating valve a cycle without pressure could occur. In addition, it would be easily possible for an operator who happened to be, e.g., in the adjusting path of the operating arrangement, to push the working cylinder back again and to reopen the operating path. This pressure sensor can also be used for detecting the manual operation of the working cylinder as referred to previously. Exceeding a certain pressure threshold, for example, when the pump is inactive, is interpreted as an indicator for the desire of a manual actuation, and subsequently the proportional pressure-regulating valve could be controlled accordingly for it to open. Also, it is possible to use such a monitor to correspondingly coordinate different points of the actuation movement, or of the further actuation process or of the controlling action of the proportional pressure-regulating valve.
In an advantageous realization of the invention the pressure sensor is arranged in or on the common supply line to the proportional pressure regulating valve, thus allowing the use of a single pressure sensor for both working chambers of the working cylinderxe2x80x94aside from this, also possible would be, of course, an apparatus consisting of two separate pressure sensors for monitoring the two sides of the working cylinder. However, as referred to above, the holding pressure could also be realized independently of a separate pressure sensor by way of (e.g. mechanical) pre-loading of the proportional pressure regulating valve.
According to a farther advantageous realization of the invention a distance sensor is arranged on the working cylinder. And the output measured by the distance sensor is forwarded to the control device. Distance sensors are often integrated in various ways in actuation apparatuses of this kind anyway, for example, for establishing if certain positions were reached, final positions and the like. With this distance sensor, while the pump is inactive, it can be determined very easily if, through a corresponding displacement of the piston of the working cylinder, a manual operation has been initiated. Following this the control of the proportional pressure regulating valve can be influenced correspondingly according to the way described above.
According to a particularly preferred realization of the invention it is envisioned that the proportional pressure regulating valve is closed when deenergized, thus allowing a simple apparatus and/or a simple hydraulic cycle. Often this will be preferred for safety reasons due to the blocking of the hydraulic actuation which occurs with this apparatus (if necessary, only up to the xe2x80x9cholding pressurexe2x80x9d).
The invention will be described in more detail in accordance with the schematically illustrated embodiments in the drawings.